Broadcast transmitting system



I ling and deals more Patented Sept 1 933 ris ' BROADCAST TRANSMITTING sYs'isM a iJulius WeinBergerQNew Yorli, N. Y ass'ignor to.

ltadio g Corporation of America, a corporation of Delaware Application September-15, 192 7 Serial Nina-219,788"

a a This invention relates to the art'of radio signaltion of the phenomenon. of fading. v Fading'may be explained as follows:

It is well known that the radiation from a simple vertical antenna, or T antenna, such as is normally used at a broadcasting station, in. various vertical directions, maybe representedbyFigjl; Here the length of vectors drawn from the point 7 represent the radiation which goes off from the antenna at varying'anglesto the'horizontal. The radiation is a maximum in a direction parallel to, the earth and decreases towards the vetrical, be-f" comingzero in. a direction directly above the an" 7 tenna.- It is also well known that transmission from a broadcasting station to a listener takes 7 n place along more thanonepath, particularly at nightyan'dit is the consensus of opinion at the present time. that fading is due to transmission which reaches-a listener simultaneously across I ground, and by means of a more-or less curved overhead path or by reflection. This is illustrated diagrammatically in Fig. 2, where T represents the location of the transmitter and R. represents" the location of the receiver.

Recent experimentshave, indicated that the overhead wave is bent down by means of a layer or-regionabout 120 miles above the earth. This height has been determinedlfor wave lengths between 301) and 500 meters, although it is probable that the height of the, downward refracting layer orregion varies with the wave length, season of the yearand with day or night. 'The worst fading then is probably due to variations of trans mission conditions in this layer, which cause the length of path of the overhead-wave to vary slightly from moment to moment. We then would have. a condition in which a variation of only one-half of a wavelength would cause the two waves at the receiving point to coincide in phase,

or be completely out of, phase, thus resulting in a signal fluctuating from a value equal to double the intensity of either wave, down to zero.

It is therefore an object of this invention to minimize or prevent transmission, of signals simultaneously by, the direct path andby reflection,

so that interference between the direct and refiec tion waves is reduced or prevented- I Itis afurther object of this invention to transmit-radio frequency impulses in sucha way that the impulses when received'will not .be capable of producing two or more out of phase fields.

Further,,it is an object of thisinvention to i utilize a predetermined path for signaltransmisspecifically with the elimina sion in a horizontaland/or vertical planeby means of a directive transmitter.

"Further, it i's an object of this invention to transmit, signals bya directpath (without re- "ine'd distance andto fiection) for a predete transmit signals by a re ted path'for-another predetermined distance. j v V 'f,"

Andit is afurthe'r objectof this invention to transmit radiofrequency impulses azt a'predetermined angle with respect'to' the horizontal. V (Finally it is an object of this invention to mitter. V a Theseandother objects of the inventionwill be readily apparent to those skilled in the art from the following description taken in connection with the accompanying-drawing in-which:

* Fig=-1 is. atransmission diagram of a" normal broadcasting station;

Fig. 2 is a diagrammatic representation of the prevent fading by employing'a directionaltrans normal path of radio frequency impulses between transmitter and receiver;

Fig. 3 is a diagrammatic showing of one em-.

bodiment of the invention;

Fig. 4 is a transmission diagram embodying the present invention;v and of a system Fig. 5 is ,a diagram showing another embodimentof' the invention.

In order to carry out my invention Iarrange the transmitting antenna system at thebroadcasting station so that radiation is confined to such an, angle, with respect to the earth, that waves are not transmitted at a steep enough angle to reach the refracting layer, roughly 120 miles high, until considerably beyond the distance at which theground wave has become largely at from transmitting to receiving points either by meansof the ground wave alone, or the overhead wave alone, but not byboth simultaneously;

To this end it is necessary to arrange the trans- .mitting antenna system so as to confinethe radi- 'tenuated. Thus transmission will be carried on ation, as 'viewed-inthe vertical planeto angles centratedin a single direction, and at limited angles td horizontal. However, viewing the radiationin the-horizontal plane, it will be noticed that-here also. the radiation is directional in nature. It is possible practically to build such an antenna systemin which the angle to either side of the'center line is degrees, in thehorizontal "plane; In the vertical plane theradia tion is confined to within 60 degreesfrom the v horizontal.

At a broadcastingstation a'series of such an-f. tennaz would be arranged, so as to have the radia'-"- tion diagrams in the horizontal plane: overlap;

A plan of a typical arrangement for this purpose is shown in Fig. 5.

. pended claims.

This ,jconsists of a radial assemblyof a number of 'structures of the type shown inFig.'4. At a coast-wise station it would not be necessary to have these antennae directed towards the sea, but only along the coast and centrated in directions which would be useful to broadcast listeners The vertical antennai sys tein;Jtvhich shown for accomplishing this-object is not the only method oi securing the desiredctype oiadirectional 'r adiation ;jand* other methods vwill readilysug' est themselvesto those skilled in the art. 'I therefore do not intend'to limit the scope of thisinyentione 't 'a's -outlined inithe ap IHaving t u claim is:

1 1.,The methodloffeliminating fading in a radio signalling system which comprises directiyely transmitting: signal impulses at a predetermined angle wi' tlifrespect to the, horizontal; said signal impulses havingfa first component which 1 travels I substantially parallel to the surface of the-earth anda asecond component which hasa trajectory I in described fiynfieimn, aha v v d angle in, a vertical plane passed through said and a second component which has a trajectory sufficiently highyto: cause the same to reach the V heaviside' layer; 'said angle being of such magnitude that the received signals at one given ;point are comprised substantially only of said first mentioned component and the received signalsf'alt a second predetermined point are 'comprised .substantially only of .said secondmentioned component and receiving one component onlyof said signals; whereby interference be? tween said components at a given pointis pre- '3. -The method of signalling by means of an aerial system including a plurality of spaced radiators energized in predetermined phase relation, which includes the steps of radiating energy from' said system, directing the energy at an systemsuch that the energy reflected from the heaviside layerreaches the earth at a distance from the radiator atwhich the ground wave becomes attenuated and receiving energy; overhone of said paths only. j V s JULIUS WEINBERGER.

components to bereceived at a given point, and 

